Metallic gasket for vacuum device and method of producing thereof

ABSTRACT

A gasket  1   3  is made of nickel, nickel alloy or stainless steel. A portion which is made a sealing face  1   s  by abutting on a knife-edge  2   b  of a joint is cut so as to form a concave groove  10.  The concave groove  10  has a structure one step lower than land portions  11   a   , 11   b  comprised of both sides  1   a . In the process from the production of the gasket to its installation, the land portions prevent the gaskets or the gasket and a rest from contacting with each other. Accordingly, no dent and no scratch is formed.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a vacuum device to be used for a semiconductor equipment, such as a thin film producing unit and an etching and to be used for another electronic industry, optical industry and an experimental unit, and more particularly, to a metallic gasket to be used for a joint for connecting a vacuum vessel and an another member, such as a viewing port, with each other, or for connecting connection members with each other in a vacuum state, and a method of producing the same.

[0002] In general, a gasket for a joint in a vacuum device is made of elastomer, such as rubber, and is made of metal. In most cases, the gasket made of elastomer is available owing to the improvement of the quality of rubber for vacuum. But, the gasket made of metal is also used in many cases, considering problems, such as airtightness to ultra high vacuum, application condition of high temperature, and gas evolved from the gasket made of elastomer.

[0003] In general, the metallic gasket has the shape of a plate or has a section in the shape of a rectangle. As shown in FIG. 7(a), a gasket in the shape of a plate 1 ₁ is held between a pair of vacuum joints 2 ₁ and 2 ₂, each having a flange 2 a and an annular knife-edge 2 b. And, bolts 3 are inserted into many holes 2 c formed at the flange 2 a so as to fasten with nuts 5, so that the knife-edge 2 b bites into both sides 1 a, 1 a of the plate-shaped gasket 1 ₁ so as to connect both joints 2 ₁ and 2 ₂ with each other, holding airtightness.

[0004] And, as shown in FIG. 7(b), a gasket 1 ₂ having a section in the shape of a rectangle is held between a pair of vacuum joint 2 ₁ and 2 ₂, each having the flange 2 a, a tapered face 2 d broadening for the outside diameter direction, and a vertical face 2 e formed at its outside diameter side end. Then, in a similar way to the above-mentioned, both joints are fastened with the bolts 3 and the nuts 5 so as to abut the tapered face 2 d on a corner portion 1 c of the gasket 1 ₂, so that the corner portion 1 c is crushed, holding the gasket 1 ₂ between the tapered face 2 d and the vertical face 2 e so as to connect both joints 2 ₁ and 2 ₂ with each other, holding airtightness.

[0005] That is, airtightness is maintained by squeezing deformation of both faces of the gasket with the knife-edge 2 b in the metallic gasket 1 ₁ in the shape of a plate, and by squeezing deformation of the corner portion 1 c of the gasket with the tapered face 2 d in the gasket 1 ₂ having a section in the shape of a rectangle. Generally, the metallic material of the gasket is copper, and aluminium may be also used.

[0006] In general, a bakable vacuum joint 2 having the knife-edge 2 b and the tapered face 2 d (generally called “con flat flange” (“Con Flat” is a trademark)) is used in combination with a gasket made of oxygen free copper. And, the goodness of spreading of the gasket made of oxygen free copper, a strength of the flange 2 a and a pressing force owing to the number of the bolts 3 are matched with one another so as to bring good results.

[0007] In recent years, the desired gasket can endure the heating of 200 through 450° which is general baking temperature in an ultra high vacuum equipment, and can have corrosion resistance even under reducing atmosphere including halogen and the like, owing to the progress of a thin film producing unit. Furthermore, the desired gasket can endure to use under the atmosphere having higher corrosion behavior wherein process gas, such as NFn, and free atom exist, owing to the execution of in-situ cleaning of an etching processing unit of semiconductor. In such a case, use of nickel, its alloy or stainless steel, having high corrosion resistance and high heat resistance, is considered as the material of the gasket.

[0008] Then, the inventors of the present invention carried out an experiment in such a manner that the gasket made of nickel, nickel alloy or stainless steel is installed on the above-mentioned vacuum joints. As the result, although airtightness could maintained in a conventional gasket made of oxygen free copper, it was difficult to maintain sufficient airtightness in the gasket made of nickel or the like, having an annular plate shape and rectangular shaped section, having the same shape, that is, the same thickness. Besides, it was difficult to get sufficient airtightness even in an experiment with a nickel gasket having a surface ground so as to get a mirror face or the gasket having a nickel base, coated with gold or silver.

[0009]FIG. 8 (a) shows an enlarged gasket surface 1 a and an abutting face 2 j of a joint 2, typically shown. As shown in FIG. 8(b), in case of the gasket made of oxygen free copper 1 cu, the abutting face 2 j of the joint and the gasket surface 1 a are made close to each other in such a manner that the abutting face 2 j of the joint is pressed on the gasket surface 1 a, and the high portions of the gasket (convex portions), a, b, c, d . . . respectively independently receive the abutting face 2 j so as to squeeze and deform, so that the lower portions (concave portions), m, n, o, p . . . are buried. On the other hand, as shown in FIG. 8(c), in case where the gasket is made of the material having low spreading, such as nickel (and its alloy, stainless steel) 1 ni, the high portions (convex portions) a, b, c, d are slightly squeezed so as to support the load, and the whole gasket surface deforms, so that the whole gasket surface deforms and is depressed, almost still maintaining the fine shape of the gasket surface in an uneven shape.

[0010] On the basis of these results, the inventors reasoned as follows. That is, even if a flaw x, such as a scrape, a scratch and a dent, is formed on the surface la of the metallic gasket in its producing process or during its transportation or its storage as shown in FIG. 9(a), the flaw x is compensated (x′) on the basis of superior malleability at the time of deformation of the gasket by the knife-edge 2 b or the tapered face by fastening the joints so as to maintain its airtightness in the case of the gasket made of oxygen free copper 1 cu, as shown in FIG. 9(b). On the contrary, in the case of the gasket made of nickel (and its alloy, and stainless steel) 1 ni, a flaw x″ remains without being squeezed by the knife-edge 2 b, communicating an inside and an outside of a vacuum device with each other in such a manner that the above-mentioned flaw x deforms in a periphery in a peripheral direction of the flaw x by the knife-edge 2 b even if the number of the bolts 3 is increased so as to generate big pressing force, and the whole including the flaw x is depressed, attended by the deformation, as shown in FIG. 9(c). On this occasion, FIG. 9 is a view typically shown, and the flaws x, x″ and the like are exaggeratedly shown. In general, the flaw x″ of FIG. 9(c) is not formed on a plane of a cross section, but is three-dimensionally formed, communicating an inside and an outside of a vacuum device with each other.

[0011] The metal having high corrosion resistance, such as nickel and stainless steel, has high hardness. Then, the action of pressing force corresponding to the hardness on a metallic gasket by increasing the number of the bolts 3 so as to increase fastening force has a bad influence upon the durability of the vacuum joints 2 ₁, 2 ₂, such as a knife-edge. At the result, the lifetime of the joint is widely shortened. Accordingly, thermal treatment, such as annealing, is preferably performed on the metal having high corrosion resistance, such as nickel, so as to lower the hardness for its use. But, metallic gaskets or a metallic gasket and a jig are put together by baking during the thermal treatment, and flaw are formed on a surface of the metallic gasket at the time of pulling them apart from each other. Then, the flaw has a bad influence upon the sealing effect of a metallic gasket.

[0012] The object of the present invention is to provide a metallic vacuum gasket having a structure so as not to form flaws on a portion of a gasket which is made a sealing face in the process from the production to the installment of a metallic gasket such that the above-mentioned problems can be solved, and a method of producing the same.

SUMMARY OF THE INVENTION

[0013] The present invention of claim 1 is metallic gasket for vacuum device, being put between vacuum joints, for sealing by being squeezed and deformed by being pressed by an abutting portion of said joint, comprising:

[0014] a sealing face to be squeezed and deformed by being pressed by said abutting portion, being thin in a thickness direction with respect to a land portion which is not abutted on said abutting portion, and said land portion provided for protecting said sealing face so as not to form a flaw on said sealing face.

[0015] According to claim 1 of the present invention, the sealing face is protected by the land portion even if the gaskets or the gasket and the jig are stuck together by baking in a thermal treatment in the producing process, or the metallic gasket is abutted on a goods rest or the gaskets are abutted on each other in its carry and its storage, or a dent or a scratch is formed on a surface of the gasket owing to the intervention of chips. Accordingly, the flaws can be prevented from being formed by peeling off the baked portions or by the abutment or by chips, thereby poor airtightness owing to the dent or the scratch on the sealing face can be avoided.

[0016] The present invention of claim 2 is the metallic gasket for vacuum device according to claim 1, wherein said metallic gasket is comprised of nickel, nickel alloy or stainless steel.

[0017] According to claim 2 of the present invention, the metallic gasket is made of nickel, nickel alloy or stainless steel, which material has high corrosion resistance. Even if it is used for a vacuum device under high corrosion resistance atmosphere, the gasket has sufficient durability. Although spreading is low and the sealing leakage owing to the above-mentioned dent or scratch is easy to occur in the above-mentioned material, the damage of the sealing face can be avoided, and sufficient airtightness can be secured with high credibility.

[0018] The present invention of claim 3 is the metallic gasket for vacuum device according to claim 1, wherein said metallic gasket is comprised of nickel, nickel alloy or stainless steel, and at least said sealing face thereof is plated with gold or silver.

[0019] According to claim 3 of the present invention, the metallic gasket is plated with gold or silver in addition to the metallic gasket comprised of nickel, nickel alloy or stainless steel having high corrosion resistance, then, the gasket can have higher corrosion resistance. Besides, airtightness can be obtained with higher credibility by both characteristics, the material characteristic by gold coating or silver coating and the shape characteristic concerning the protection of the sealing face by the land portion.

[0020] The present invention of claim 4 (see FIGS. 1(a), (b), (c) and FIG. 2 for instance) is the metallic gasket for vacuum device according to claim 1, wherein an abutting portion of said joint for said vacuum device is comprised of a knife-edge, said metallic gasket has plate shape having both sides, and a portion abutting on said knife-edge including said sealing face of said both side faces, is formed by a concave groove or a stepped portion lower than said land portions comprised of said both sides.

[0021] According to claim 4 of the present invention, the portion abutting on the knife-edge, including the sealing face of both sides of the metallic gasket having a plate shape, is formed as a concave groove or a stepped portion lower than the land portion comprised of both sides. Then, the portion contacting with the knife-edge including the sealing face is protected by the land portion, and airtightness can be secured with high credibility.

[0022] The present invention of claim 5 (see FIG. 1(d) and FIG. 3 for instance) is the metallic gasket for vacuum device according to claim 1, wherein an abutting portion of said joint of said vacuum device is comprised of a tapered face, said metallic gasket has an almost rectangular section, and a portion which is made said sealing face by abutting on said tapered face, including a corner portion on inner diameter side is obliquely cut off.

[0023] According to claim 5 of the present invention, the portion abutting on the tapered face of a joint so as to be a sealing face, including a corner portion on the inner diameter side is obliquely cut off and is protected in the metallic gasket having a section in almost rectangular shape. Accordingly, airtightness can be secured with high credibility.

[0024] The present invention of claim 6 (see FIG. 4 for instance) is the metallic gasket for vacuum device according to claim 1, wherein at least said portion which is made said sealing face is formed by rotation cutting streaks having fine pitch.

[0025] According to claim 6 of the present invention, the portion which is made the sealing face is formed by rotation cutting streaks having thin pitch, the rotation cutting streaks are pressed almost along the abutting portion on the annular joint side, such as the knife-edge and the tapered face so as to squeeze and deform the projecting portion of the streaks by the abutting portion, thereby airtightness can be secured with higher credibility.

[0026] The present invention of claim 7 (see FIG. 5 for instance) is a method of producing a metallic gasket for vacuum device, said gasket being put between joints for vacuum device, for sealing by being squeezed and deformed by being pressed by an abutting portion of said joint, comprising:

[0027] a cutting process for cutting so as to have a sealing face being squeezed and deformed by being pressed by said abutting portion, being thin in a thickness direction with respect to a land portion which is not abutted on said abutting portion, and

[0028] a thermal treatment process for performing thermal treatment for adjusting hardness in vacuum after said cutting process.

[0029] According to claim 7 of the present invention, the hardness of the metallic gasket can be properly adjusted by heat treatment, and oxidation of the metallic gasket can be inhibited and the gas included in the gasket material can be removed since the heat treatment is performed in vacuum, so as to improve the efficiency of the metallic gasket. Since the cutting process is performed before the heat treatment process, furthermore, the hardness of the gasket can be made proper by subsequent heat process even if the surface of the gasket is hardened by the cutting machining.

[0030] Even if the metallic gaskets or the metallic gasket and a jig are stuck together by baking in heating in the heat treatment process, the baked portion is the land portion, and the flaws of the baked portions by peeling off with a tool and the flaws formed by an appliance at the time of peeling off are all on the land portion. The sealing face having no flaw is maintained in addition to the adjustment of hardness by the heat treatment, and the metallic gasket having high sealing efficiency and superior credibility can be provided.

[0031] The present invention of claim 8 is the method of producing said metallic gasket for vacuum device according to claim 7, wherein said metallic gasket is made of nickel, and hardness of said metallic gasket is adjusted to Vickers hardness 75 to 95 Hv by annealing in said heat treatment process.

[0032] According to claim 8 of the present invention, the metallic gasket is made of nickel, and the gasket is softened by annealing in the heat treatment process so as to have Vickers hardness 75 to 95 Hv. Then, big fastening force is not necessary for the joint for the vacuum device, and the metallic gasket having sufficient sealing function and corrosion resistance without damaging the lifetime of the joint can be obtained.

[0033] The present invention of claim 9 is the method of producing said metallic gasket for vacuum device according to claim 7, wherein said metallic gasket is made of stainless steel, and hardness of said metallic gasket is adjusted to Vickers hardness 120 to 180 Hv by annealing in said heat treatment process.

[0034] According to claim 9 of the present invention, stainless steel having high corrosion resistance which is relatively cheap is applied for the gasket as metallic material, and the gasket is softened by annealing in a heat treatment process so as to get Vickers hardness 120 to 180 Hv. Then, the metallic gasket having corrosion resistance which is practicable and cheap can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035]FIG. 1 is a view for showing a sectional shape of a metallic gasket according to the present invention, and (a) through (d) show embodiments different from one another;

[0036]FIG. 2 is a partial sectional view for showing such a state that the metallic gasket of the present invention which is a gasket in the shape of a plate is applied to a vacuum joint;

[0037]FIG. 3 is a partial sectional view for showing such a state that the metallic gasket of the present invention which is a gasket having a section in the shape of a rectangle is applied to the vacuum joint;

[0038]FIG. 4 is an enlarged view for showing a sealed portion, (a) is a sectional view for showing a concave groove portion sealed by a knife-edge and (b) is a sectional view for showing cut off portion sealed by a tapered face;

[0039]FIG. 5 is a view for showing a method of producing the metallic gasket according to the present invention;

[0040] FIGS. 6(a), (b) are views, each showing an embodiment of a routine of thermal treatment different from the other;

[0041]FIG. 7 is a view for showing the vacuum joints using a conventional metallic gasket, (a) is a sectional view with the gasket in the shape of a plate and (b) is a sectional view with the gasket having the section in the shape of a rectangle;

[0042]FIG. 8 is an enlarged view for typically showing a relation between a surface of the gasket and a flange face of the joint, (a) shows the surface of the gasket and the flange face apart from each other, (b) shows such a state that a gasket made of oxygen free copper is pressed on the flange face and (c) shows such a state that a gasket made of nickel or stainless steel is pressed on the flange face; and

[0043]FIG. 9 typically shows a relation between a sealing face and the knife-edge when flaws are formed on the gasket, (a) is an enlarged view for showing the sealing face of the gasket, (b) is an enlarged view for showing a case of the gasket made of oxygen free copper and (c) is an enlarged view for showing a case of the gasket made of nickel or stainless steel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] Embodiments of the present invention will now be explained hereinafter, referring to drawings. FIG. 1 is a view for showing a section of a metallic gasket, (a) through (c) relate to a plate shape sealed by a knife-edge as shown in FIG. 2 (FIGS. 7(a)), and (d) relates to a rectangular sectional shape sealed by a tapered face as shown in FIG. 3 (FIG. 7(b)). All of these is annularly formed if they are seen from their top.

[0045] The metallic gaskets as shown in (a) through (c) of FIG. 1 relate to a gasket in the shape of a plate having both sides 1 a, 1 a which are comprised of flat faces (see 1 ₁ in FIG. 7(a) of a conventional gasket). In a metallic gasket 1 ₃ as shown in (a), a sealing face 1 s to be made by abutting on the knife-edge is formed as a concave groove 10 by turning cutting machining. The concave grooves 10 of both sides have a structure which is lower one step in comparison with land portions 11 a, 11 b of both sides in a diameter direction, which are not deeply cut, that is, a structure thin in a thickness direction.

[0046] A metallic gasket 1 ₄ as shown in FIG. 1(b) is formed in such a manner that both sides 1 a, 1 a of the outside diameter side are left so as to be the land portions 11 a, the whole inner diameter side including the sealing face 1 s portion is cut by rotation cutting machining so as to form a stepped structure one step lower rather than the land portion, and a stepped portion 12 on the inner diameter side has a structure thin in the thickness direction rather than the annular land portions 11 a on the outer diameter side comprised of both sides 1 a, 1 a. In contrast to FIG. 1(b), a metallic gasket 15 as shown in FIG. 1(c) is formed in such a manner that both sides 1 a, 1 a of the inner diameter side are left so as to be land portions 11 b, the whole outer diameter side including the sealing face 1 s portion is cut by rotation cutting machining so as to form a stepped structure 13 one step lower rather than the land portion, and a stepped portion 13 on the outer diameter side has a structure thin in the thickness direction rather than the annular land portions 11 b on the inner diameter side comprised of both sides 1 a, 1 a.

[0047] A metallic gasket 1 ₆ as shown in FIG. 1(d) has a section in the shape of a rectangle, in this gasket, the corner portion on the inner diameter side (1 c; see FIG. 7(b)) is abutted on the tapered face so as to become a sealing face (see 1 ₂ of FIG. 7(b) which shows a conventional gasket). A portion 15 including the corner portion (1 c) which becomes the sealing face is obliquely cut off by the rotation cutting machining, and the portion 15 has a structure thin in the thickness direction with respect to land portions 11 c comprised of both sides 1 f, 1 f.

[0048] The metallic gaskets 1 ₃ through 1 ₆ as shown in FIG. 1 are formed by nickel, nickel alloy, or stainless steel. Of nickel, pure nickel wherein amount of impurity is relatively small is preferable as gasket member, but nickel alloy may be also available. As nickel alloy, inconel is firstly preferable, secondly incoloy, and thirdly monel. And, as stainless steel, SUS of JIS, which number is three hundred and more, and less four hundred, is preferable in non-magnetism, corrosion resistance, weldability, processability, gas evolution characteristic and the like. But, another austenite system stainless steel may be also available.

[0049] Next, a method of producing the metallic gaskets 1 ₃ through 1 ₆ will now be explained, referring to FIG. 5. Firstly, a nickel plate or a stainless plate having a predetermined thickness is purchased or a plate member is formed by processing a round bar or pipe member. Generally, annealing has already been executed on (pure) nickel plate at the stage where it is sold on the market, and the nickel plate is softened into 120 through 150 Hv. Stainless steel has (Vickers) hardness of 300 Hv or so.

[0050] And, the above-mentioned plate member is cut in a dimension easy to machine as a metallic gasket (cutting process P1). A piece of the plate member cut is cut in its surface with a turning cutting machine, such as a lathe (cutting process P2). To be more precise, in order to get the metallic gaskets 1 ₃ through 1 ₆ as shown in FIG. 1, cutting machining (turning cutting machining) is performed on its both sides with a lathe so as to remove flaws on the surface of the plate member. In certain circumstances, grinding machining is performed, and furthermore, polishing machining is performed such that the surface can be formed in a smooth face, such as a specular face. Furthermore, cutting machining is performed with a lathe on the piece of the plate member which surface is cut so as to form the concave groove 10 (FIG. 1(a)), the stepped portion 12 on the inside diameter side (FIG. 1(b)), the stepped portion 13 on the outside diameter side (FIG. 1(c) and the cut off portion 15 (FIG. 1(d)). In the final process of the cutting process (P2), streaks 16 having thin pitch are formed on these concave groove, the stepped portion and the cutting off portion by making feed speed and depth of cut of a cutting tool small, as shown in FIGS. 4(a) and (b). The streak 16 is formed in the shape of a spiral having concentric circle if it is seen from the front (if it is seen from the upper hand of the figure in (a) or if it is seen from the right direction of the figure in (b)).

[0051] Since the metallic gaskets 1 ₃ through 1 ₆ are formed by the turning cutting machining with a lathe one by one, these gaskets are arranged on a products rest next to a lathe when cutting finishes or the gaskets are piled at the time of their transportation and storage. On this occasion, the finished gasket products is abutted on the products rest or the gasket products are abutted on each other, so that dents may be formed on the sides 1 a and 1 f on the basis of the abutment between the metals, or chips or so intervene on the rest or between the products, so that scratches may be formed on the surface.

[0052] Thereafter, the metallic gasket material cut is cleaned (cleaning process P3), and then, is entered in a vacuum vessel. And, it is heated to a predetermined temperature so as to perform thermal treatment, such as annealing (thermal treatment process P4). The thermal treatment in vacuum is for prevention of the oxidation of the metallic gasket material under high temperature circumstances and for removal of gas included in the material. The nickel is softened so as to have Vickers hardness of 75 through 95 Hv, preferably 80 through 89 Hv (80 level) by the annealing. The stainless steel is softened so as to have Vickers hardness of 120 through 180 Hv, and 80 through 89 Hv as most preferable sealing member. In stainless steel, it is generally likely that coarsening arises if it is softened to the hardness preferable as the sealing member. So, the hardness of 120 through 130 Hv is preferable, taking the balance with crystal grain into consideration.

[0053] And, the metallic gasket thermally treated is inspected, packed and shipped out (P5). Since the above-mentioned thermal treatment process P4 is executed after the cutting process P2, the hardness softened by thermal treatment is maintained in the metallic gasket. That is, it is unlikely that the material softened by thermal treatment is hardened by cutting machining and softening into predetermined hardness by thermal treatment means nothing.

[0054] Next, an embodiment of the thermal treatment process will now be explained.

[0055] (Embodiment 1)

[0056] Metallic Gasket Material;

[0057] (pure) Nickel (Ni 99.0%, other is impurity)

[0058] Degree of Vacuum . . . 10⁻⁴-10⁻⁶ Torr, preferably, the level of 10⁻⁴ Torr or lower

[0059] Thermal treatment . . . Temperature is increased to 700 through 850° C. and is maintained thirty minutes so as to cool in a furnace (see FIG. 6(a)). On this occasion, the time of temperature up is thirty minutes or so, and the time of temperature down is three to five hours or so, and these are changeable by the size of a furnace (heat capacity) and the quantity of goods to be processed. If the temperature is 250° C. or lower, the goods can be taken out of a furnace so as to anneal with air.

[0060] If the temperature to be increased is 850° C. or more, crystal grain becomes big due to recrystallization, then sealing efficiency and corrosion resistance are not sufficiently exhibited. If the temperature is 700° C. or lower, softening of Ni material is insufficient.

[0061] (Embodiment 2)

[0062] Metallic Gasket Material;

[0063] 18-8 stainless steel (SUS316L, SUS304L)

[0064] Degree of Vacuum . . . 10⁻⁴-10⁻⁶ Torr, preferably, the level of 10⁻⁴ Torr or lower

[0065] Thermal treatment . . . Temperature is increased to 900 through 1100° C. and is maintained thirty minutes -three hours so as to cool in a furnace (see FIG. 6(b)). On this occasion, it is similar to the above-mentioned embodiment 1, but the time of temperature down is taken one hour or so extra since the temperature to be processed is higher in comparison with Ni processing time.

[0066] If the temperature to be increased is 1100° C. or more, crystal grain becomes big due to recrystallization, then sealing efficiency and corrosion resistance are not sufficiently exhibited. If the temperature is 900° C. or lower, softening of SUS material is insufficient.

[0067] The above-mentioned thermal treatment process is performed, piling the metallic gasket materials on each other in a vacuum vessel, or arranging them on a jig. At this time, the temperature of the metallic gasket material is increased, and the materials or the material and a jig may be stuck together by baking. At this time, the metallic gaskets or the metallic gasket and the jig which are stuck together are peeled off each other with a tool, such as a driver. Flaws may be formed on the metallic gasket by the above-mentioned baking or peeling off. But, the flaws are formed on the land portions 11 a, 11 b, 11 c which abut on each other when the metallic gasket materials are piled on each other, or arranged on a jig, and are not formed on the sealing face 1 s.

[0068] Although flaws are formed on the metallic gaskets 1 ₃ through 1 ₆ due to the dent, the scratch, the baking or the peeling off, the flaws are formed on the land portions 11 a, 11 b, 11 c capable of contacting with a rest or a jig, or the land portions contacting with each other when the products are contacted with each other. And the concave groove 10, the stepped portions 12, 13 and the cutting off portion 15 including the sealing face 1 s, concaved rather than the land portion (thin in the thickness direction) are protected by the land portions. That is, the concave groove, the stepped portion and the cutting off portion are protected without having flaws, such as the scratch and the dent, thereon by contacting the land portion with the rest or the jig or by contacting the products with each other in the land portions.

[0069] In the shapes of the gasket 1 ₃ through 1 ₆ as shown in FIGS. 1(a), (b), (c) and (d), the portion including the sealing face 1 s is protected by the land portion. As their protecting effects, the gasket 1 ₃ of FIG. 1(a) is most superior, and subsequently, the gasket 1 ₆ of FIG. 1(d), the gasket 1 ₄ of FIG. 1(b) and the gasket 1 ₅ of FIG. 1(c) in order.

[0070] The metallic gaskets 1 ₃ through 1 ₆, for instance, the gasket 1 ₃ is used for the vacuum joint 2 ₁, 2 ₂ (bakable flange having a knife-edge) similar to a conventional one, as shown in FIG. 2 (On this occasion, the other plate shaped gaskets 1 ₄, 1 ₅ are also similar, so the explanation is omitted). The gasket 1 ₃ is put between both joints 2 ₁, 2 ₂ so as to position a knife-edge 2 b in the concave groove 10 including its sealing face 1 s. In this state, many bolts 3 and many nuts 5 are fastened, and the knife-edge 2 b bites into the sealing face 1 s so as to seal and connect both joints with each other. In this state, the sealing face 1 s of the gasket 1 ₃ which is made of the material wherein spreading is low in comparison with a conventional copper, such as nickel, nickel alloy and stainless steel, positions in the concave groove 10 protected by the land portions 11 a, 11 b. Then, both joints are sealed with sufficient airtightness without a scratch and a dent, as mentioned before.

[0071] In a similar way, the gasket 1 ₆ as shown in FIG. 1(d) is put between both joints 2 ₁, 2 ₂ so as to position the cutting off portion 15 including its sealing face 1 s at a tapered face 2 d, as shown in FIG. 3. In this state, many bolts 3 and many nuts 5 are fastened such that an outer diameter side 1 g of the gasket 1 ₆ abuts on a vertical face 2 e of the joint and the sealing face 1 s is squeezed by the tapered face 2 d. Accordingly, both joints are sealed and connected with each other. In this state, the sealing face 1 s of the gasket 1 ₆ which is made the material wherein spreading is low, such as nickel, positions on the cutting off portion 15 protected by the land portions 11 c, 11 c. Then, both joints are sealed with sufficient airtightness without a scratch and a dent, as mentioned before.

[0072] Furthermore, the concave groove 10 (the stepped portions 12, 13 are also similar) and the cutting off portion 15 including the sealing face 1 s are comprised of streaks 16 having a fine pitch in the shape of almost concentric circle (exactly speaking, spiral), as shown in FIGS. 4(a) and (b). Then, the annular knife-edge 2 b and (the abutting portion of) the tapered face 2 d are pressed along the streaks. Then, the projected top portion of the streaks in the shape of almost concentric circle of the portion contacted so as to be pressed is relatively easily squeezed and deformed along the knife-edge and the abutting portion of the tapered face. Even if small flaws are formed, the flaws are compensated by the projected portions of the streaks 16 so as to certainly seal.

[0073] The above-mentioned metallic gaskets 1 ₃ through 1 ₆ are comprised of the material wherein corrosion resistance is high, such as nickel, nickel alloy and stainless steel. Even if a vacuum device is used under the atmosphere of high corrosion resistance, such as halogen, NF₃ gas, free hydrogen, the gasket has sufficient durability. Furthermore, in even the gasket comprised of corrosion resistance material, such as nickel and stainless steel, thermal treatment is performed in the process after a cutting process, and the gasket is maintained at a predetermined hardness softened. Even if the pressing force on the gasket by fastening of the bolts 3 and the nuts 5 is relatively low, the knife-edge 2 b and the tapered face 2 d bite into the sealing face 1 s of the gasket so as to exhibit high sealing efficiency and to reduce the damage of the knife-edge 2 b and the tapered face 2 d of the joints 2 ₁ and 2 ₂ and to improve the durability of the joint 2 ₁ and 2 ₂.

[0074] On this occasion, the shape of the metallic gasket is shown in FIGS. 1(a), (b), (c) and (d) in the above-mentioned embodiment. But, the shape is not limiting, but any shape is available as long as the portion which is made a sealing face is lower than the land portion (thin in the thickness direction). Besides, the present embodiment refers to the material of the metallic gasket, such as nickel, nickel alloy and stainless steel. But, the material is not limiting, but another materials, such as the material wherein corrosion resistance is high or spreading is low, are similarly applicable.

[0075] Furthermore, the metallic gasket may be formed with the above-mentioned material and with the above-mentioned shape, and the whole surface or the concave groove, the stepped portion or the cutting off portion including the sealing face only may be plated with gold or silver such that the plating width is relatively thick. It is not necessary to produce this type of the whole gasket with gold or silver which is expensive. That is, corrosion resistance efficiency and sealing efficiency can be further improved by both effects, that is, by the material characteristic having gold and silver and by the shape characteristic wherein no flaws are formed on the concave groove, the stepped portion and the cutting off potion which are made the sealing faces protected by the land portions.

[0076] The present invention is explained on the basis of the embodiment heretofore. The embodiments which are described in the present specification are illustrative and not limiting. The scope of the invention is designated by the accompanying claims and is not restricted by the descriptions of the specific embodiments. Accordingly, all the transformations and changes belonging to the claims are included in the scope of the present invention. 

1. Metallic gasket for vacuum device, being put between vacuum joints, for sealing by being squeezed and deformed by being pressed by an abutting portion of said joint, comprising: a sealing face to be squeezed and deformed by being pressed by said abutting portion, being thin in a thickness direction with respect to a land portion which is not abutted on said abutting portion, and said land portion provided for protecting said sealing face so as not to form a flaw on said sealing face.
 2. The metallic gasket for vacuum device according to claim 1, wherein said metallic gasket is comprised of nickel, nickel alloy or stainless steel.
 3. The metallic gasket for vacuum device according to claim 1, wherein said metallic gasket is comprised of nickel, nickel alloy or stainless steel, and at least said sealing face thereof is plated with gold or silver.
 4. The metallic gasket for vacuum device according to claim 1, wherein an abutting portion of said joint for said vacuum device is comprised of a knife-edge, said metallic gasket has plate shape having both sides, and a portion abutting on said knife-edge including said sealing face of said both side faces, is formed by a concave groove or a stepped portion lower than said land portions comprised of said both sides.
 5. The metallic gasket for vacuum device according to claim 1, wherein an abutting portion of said joint of said vacuum device is comprised of a tapered face, said metallic gasket has an almost rectangular section, and a portion which is made said sealing face by abutting on said tapered face, including a corner portion on inner diameter side is obliquely cut off.
 6. The metallic gasket for vacuum device according to claim 1, wherein at least said portion which is made said sealing face is formed by rotation cutting streaks having pine pitch.
 7. A method of producing a metallic gasket for vacuum device, said gasket being put between joints for vacuum device, for sealing by being squeezed and deformed by being pressed by an abutting portion of said joint, comprising: a cutting process for cutting so as to have a sealing face being squeezed and deformed by being pressed by said abutting portion, being thin in a thickness direction with respect to a land portion which is not abutted on said abutting portion, and a thermal treatment process for performing thermal treatment for adjusting hardness in vacuum after said cutting process.
 8. The method of producing said metallic gasket for vacuum device according to claim 7, wherein said metallic gasket is made of nickel, and hardness of said metallic gasket is adjusted to Vickers hardness 75 to 95 Hv by annealing in said heat treatment process.
 9. The method of producing said metallic gasket for vacuum device according to claim 7, wherein said metallic gasket is made of stainless steel, and hardness of said metallic gasket is adjusted to Vickers hardness 120 to 180 Hv by annealing in said heat treatment process. 